Residents of Libby, MT, have been exposed to asbestiform minerals (Libby amphibole, or LA) including tremolite and other regulated amphibole types as well as unregulated fibers including winchite and richterite (Meeker et al. 2003) since the 1920s through the operation of a vermiculite mine and processing plant until 1990, when the mine was closed. Exposure prior to 1990 had been occupational, para-occupational (via residence with an LA-exposed worker) and/or environmental; the main exposure pathways have been detailed by Peipins (2003). Since closure of the mine, people in the Libby area have continued to be exposed to residual asbestos contamination principally via disturbance of LA-containing materials in place, mitigated by site cleanup efforts begun by the EPA in 2000. The health consequences of exposure to LA in the Libby community have been summarized by the ATSDR (2003) and include increased rates of asbestosis and pleural scarring, increased mortality from asbestosis, lung cancer and mesothelioma, and an increase in the prevalence of autoimmune antibody abnormalities and diagnosed systemic autoimmune diseases. The planned studies seek to address several questions regarding the health consequences of exposure to LA: 1) the possible particular risk of exposure during childhood, including effects at low cumulative exposure levels; 2): the unusually rapid and impairing character of LA-related pulmonary disease; and 3) non-pulmonary health effects, specifically autoimmune disorders. The High School Graduates Study will investigate the consequences of exposure to LA that occurs only during childhood and adolescence and will permit an evaluation of the human health effects of exposure at low cumulative levels, an issue of considerable importance to the development of a Baseline Risk Assessment and determinations of levels of residual contamination of the environment that can be considered safe for the Libby community, including children. There is considerable clinical evidence that pulmonary disease associated with exposure to LA has a more aggressive course with more rapid progression of scarring and loss of lung function than is seen among workers heavily exposed to commercially used forms of asbestos. The CT Progression Study will evaluate whether asbestos-related scarring of the lung parenchyma and/or pleura evident on chest CT scans following only environmental exposure to LA progresses more rapidly than is seen in long-term asbestos insulators with high cumulative exposure levels. Non-pulmonary consequences of LA exposure, i.e. autoimmune abnormalities and diseases, will be evaluated in the Autoimmune Outcomes Study by assessing the prevalence of autoimmune antibody abnormalities and physician-diagnosed autoimmune diseases in relation to exposure measures.